I feel like Columbine being eclipsed by Stoneman Douglas also played a part in the fall of Columbine's relevance among school shooters. Now they're being forced to branch out, find more people to copy.
Your line about Columbine not being as "revolutionary" as other shootings is probably correct, which would lead to less school shootings happening in general. For instance, if Christchurch didn't happen, then considering that Payton Gendron wrote about considering murder-suicide when he was hospitalized prior to his redpilling, he might've tried to follow in Harris and Klebold's footsteps. Instead, he tried to emulate Brenton Tarrant.